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Dams and river crossings often block the migration routes of stream-dwelling fish in addition to their better-known effects preventing salmon from spawning in upper river reaches. Relatively little is known about the movements of mountain whitefish (Prosopium williamsoni) in the Pacific Northwest, despite their widespread distribution. In the upper Cedar River, Washington, mountain whitefish had been absent above the Landsburg Dam, constructed in 1901, until a fish ladder was built in 2004 that allowed their upstream passage.

Whooping cranes are endangered and slowly recovering from a low point of just 15 birds and one migratory population in the wild. New efforts have established an eastern second migratory population from captive-bred birds, although not without some difficulty, since migration routes are learned from other adults. In the eastern population two methods were used to teach a new migration pathway: imprinting cranes on ultralight aircraft on the ground, which would lead the cranes to an overwintering destination; or imprinting them to follow older whooping cranes or wild sandhill cranes when they migrate.

Smallmouth bass are native to much of the midwestern USA and central Canada, but have been introduced to 41 states and 20 countries. While they are sought-after angling targets, they also are voracious predators of small fish and crayfish, which is of particular concern given their taste for baby salmon and trout. Thus it is crucially important for management and conservation to detect which streams have been occupied by smallmouth bass.

Many fish species repeatedly migrate from feeding areas to spawning areas, and their migration pathways could be innate or learned. Two possible models are examined for learning of these migration pathways: the Diffusion Model holds that fish head to spawning site near where they themselves hatched; while the Go With the Old Fish Model involves young fish joining schools of older fish, and learning migration pathways from the older fish.

Citizen science is when members of the public directly work with scientists on a particular question or issue. Participation can range from a large number of single interactions to repeated and complex sampling that requires substantial training. A new paper now explains how to train participants, validate the collected data, and produce rigorous scientific papers from the outcomes. Key highlights include the need to increase the quality of data when designing a project, and to apply quality control afterwards to check for issues with the collected data.

Increasing human output of carbon dioxide results in higher temperatures and in ocean acidification—the lowering of ocean pH and other chemical changes. Oysters are threatened by ocean acidification, while eelgrass may benefit from the higher carbon dioxide levels in the water. A new laboratory study asks whether culturing Pacific oysters (Crassostrea gigas) together with eelgrass (Zostera marina) can help both out.

Many lakes are important sources of water for agriculture and other purposes, while also supporting diverse ecosystems. In a new study, a comparison is made between the food webs of two natural lakes that were dammed early in the 20th century. The neighboring lakes are nearly identical except that one (Lake Keechelus) experiences rapid drawdown of water beginning early summer while the other (Lake Kachess) remains fuller and fluctuates less in water height during summer, but is lowered to a lesser extent beginning early fall.

Formal stock assessments are conducted for many large and valuable fisheries, but these typically require reliable catch data, estimates of trends in fish numbers, and age data from caught fish. In data-poor fisheries, these kinds of data are not available, resulting in difficulties in assessing whether they are overfished or sustainably fished. Now a new model called LIME has been developed that accounts for variability in recruitment (the number of baby fish produced each year), and can assess status from samples of the lengths of fish in each year, together with whatever additional information is available.

Many populations of native steelhead trout in the Pacific Northwest US are threatened by disease, habitat loss, poor ocean survival, and genetic mixing with hatchery steelhead trout. Steelhead are a form of rainbow trout that migrate out to the ocean when young, and return to spawn, just like many salmon species. Hatchery-produced steelhead have lower survival in the wild because they become less afraid of predators; one of the resulting concerns is that interbreeding between hatchery and wild steelhead will erode the natural fitness of wild steelhead and hinder their recovery.

Salmon returning to streams and lakes in Southeast Alaska are affected greatly by water temperatures both in winter and summer, and these temperatures are projected to increase given climate warming. Changes in water temperature affects the time it takes for salmon eggs to hatch and emerge, and the timing of salmon returning to each stream, as they seek to avoid dangerous peak stream temperatures.